Battery cell and battery pack

Abstract

The application relates to the technical field of batteries and discloses a battery cell and a battery pack. The battery cell comprises a shell, a pole group arranged in the shell, the pole group having a pair of narrow sides arranged opposite to each other along an X direction and a pair of large surfaces arranged opposite to each other along a Y direction, a first insulating film, when the number of the pole groups is one, at least part of the first insulating film being wrapped around the outside of the single pole group along the circumference of the X-Y plane, when the number of the pole groups is multiple, at least part of the first insulating film being wrapped around the outside of the multiple pole groups along the circumference of the X-Y plane, and a fireproof coating arranged on the first insulating film, at least part of the fireproof coating being arranged opposite to the narrow sides. The application can effectively block heat transfer and flame spread when thermal runaway occurs in the single battery cell by arranging the fireproof coating opposite to the side wall of the pole group on the first insulating film.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a battery cell and battery pack. Background Technology

[0002] New energy batteries, due to their high energy density and long cycle life, have been widely used in new energy vehicles, energy storage, and other fields. However, when conventional new energy batteries experience thermal runaway propagation, violent internal reactions and rapid ignition can easily occur. The resulting high-temperature, high-pressure products can easily be ejected from both sides of the cell, and the high-temperature flames can easily ablate and penetrate the cell casing, igniting adjacent cells and forming a chain reaction of thermal runaway. This process accelerates the rate of thermal runaway propagation, causing the battery system to quickly enter an uncontrollable state, reducing the overall safety of the cells and the battery system, and posing a significant safety risk. Therefore, how to effectively suppress the rapid chain reaction caused by thermal runaway in cells has become a critical technical problem that needs to be solved to improve the safety performance of battery packs. Summary of the Invention

[0003] This invention provides a battery cell and a battery pack to solve the problem that when a single battery cell experiences thermal runaway, it can easily lead to successive thermal runaway of adjacent cells, affecting the safety of the battery pack.

[0004] In a first aspect, the present invention provides a battery cell, comprising: case; An electrode assembly is disposed within the housing, the electrode assembly having a pair of narrow side surfaces opposite each other along the X direction and a pair of large surfaces opposite each other along the Y direction; A first insulating film, when the number of electrode groups is one, at least a portion of the first insulating film wraps around the outside of the single electrode group circumferentially along the XY plane; when the number of electrode groups is multiple, at least a portion of the first insulating film wraps around the outside of multiple electrode groups circumferentially along the XY plane. A fire-retardant coating is disposed on the first insulating film, at least a portion of which is disposed opposite to the narrow side surface.

[0005] Beneficial effects: By setting a fire-retardant coating on the first insulating film opposite to the narrow side, the present invention can form a heat-insulating and flame-retardant barrier on the narrow side. When a single cell experiences thermal runaway, it can effectively prevent the transmission and spread of high temperature and flame to adjacent cells, suppress the chain reaction of thermal runaway, and thus improve the overall safety of the cell and battery pack.

[0006] In one alternative embodiment, the fire-retardant coating is disposed on the side of the first insulating film close to the electrode assembly; and / or, the fire-retardant coating is disposed on the side of the first insulating film away from the electrode assembly.

[0007] Beneficial effects: By setting a fire-retardant coating on one or both sides of the first insulating film, the present invention can form an effective heat-insulating and flame-retardant barrier between the electrode group and the shell when thermal runaway occurs in the battery cell, reducing the direct impact of high-temperature flames on the shell, reducing the risk of the shell being burned through, thereby effectively inhibiting the spread of flames to adjacent battery cells, slowing down the thermal runaway propagation rate, and improving the overall safety of the battery cell and battery module; at the same time, the fire-retardant coating and the first insulating film are combined to ensure the insulation protection function while taking into account the structural compatibility, which is conducive to meeting the requirements of battery cell coating and assembly process.

[0008] In one alternative implementation, along the X direction, the orthographic projection of the fire-retardant coating toward the narrow side falls within the orthographic projection range of the narrow side.

[0009] Beneficial effects: Along the X direction, the present invention sets the orthographic projection of the fire-retardant coating toward the narrow side to fall within the orthographic projection range of the narrow side. This can effectively block the high-temperature flames and heat splashed from the narrow side during thermal runaway, preventing the flames from burning through the shell and spreading to adjacent cells. It can also avoid ineffective application of the fire-retardant coating, reasonably control the material and application range of the fire-retardant coating, and ensure the structural compactness of the cell while ensuring the protective effect. It can also reduce problems such as decreased flexibility and easy cracking and material loss under stress caused by excessive application of the fire-retardant coating, ensuring the structural stability of the fire-retardant coating during cell assembly and use, and ensuring that the heat insulation and flame retardant effect continues to be effective.

[0010] In one optional embodiment, on the YZ plane, the distance between the four perimeters of the fire-retardant coating and the adjacent narrow side edge is w, where w ranges from 1mm ≤ w ≤ 30mm.

[0011] Beneficial Effects: This invention limits the value of the interval w to between 1mm and 30mm, enabling the fire-retardant coating to adapt to the battery cell housing structure and avoid assembly damage while ensuring the effectiveness of heat insulation and flame retardancy protection, further improving the reliability of thermal runaway protection for the battery cell. Specifically, when w is not less than 1mm, it can effectively prevent interference and squeezing between the electrode group and the housing R-angle during battery cell assembly, which would cause the fire-retardant coating to fall off or break, ensuring the structural integrity and stable performance of the fire-retardant coating. When w is not greater than 30mm, it can ensure that the fire-retardant coating provides sufficient coverage and protection for the narrow side of the electrode group, preventing high-temperature flames and heat from escaping through the protective gap during thermal runaway due to insufficient coverage, effectively blocking side-sprayed flames from burning through the housing and spreading heat to adjacent battery cells, and suppressing the occurrence of thermal runaway chain reactions. In one alternative embodiment, the thickness of the fire-retardant coating along the X direction ranges from 0.05 mm to 0.5 mm.

[0012] Beneficial Effects: This invention limits the thickness of the fire-retardant coating to between 0.05mm and 0.5mm, balancing the heat insulation and flame retardant effects with structural flexibility. Specifically, when the thickness is not less than 0.05mm, it forms an effective protective barrier against thermal runaway high-temperature flames and heat, ensuring effective isolation of high-temperature heat sources sprayed from the narrow side of the electrode assembly, preventing flames from burning through the casing and spreading to adjacent cells. When the thickness is not greater than 0.5mm, it ensures good flexibility of the fire-retardant coating, preventing cracking and material loss during cell assembly and use due to excessive thickness, ensuring the structural integrity and adhesion stability of the fire-retardant coating, while avoiding excessive coating thickness that increases the overall volume of the cell and affects its structural compactness. Under the premise of ensuring the effective performance of the core fire protection effect, it adapts to the structural design and actual application needs of the cell, improving the stability and reliability of the fire-retardant coating protection.

[0013] In one alternative embodiment, the first insulating film includes a plurality of insulating diaphragms, which are sequentially stacked along their thickness direction and wrapped around the outer side of one or more of the electrode groups along the XY plane.

[0014] Beneficial effects: This invention sets the first insulating film as multiple insulating membranes stacked sequentially along the thickness direction to wrap around the periphery of the electrode assembly. On the one hand, this forms a multi-layered insulating protective structure, improving the insulation performance between the electrode assembly and the casing, and effectively reducing the risk of leakage and short circuits inside the battery cell. On the other hand, the multi-layered insulating membranes provide a more stable adhesion substrate for the fire-retardant coating, and the layered structure can disperse the external force compression and friction during battery cell assembly and use, reducing the problem of peeling and damage to the fire-retardant coating due to substrate damage, and ensuring the stable performance of the fire-retardant coating's heat insulation and flame retardant effect. At the same time, the multi-layered insulating membrane design can form a synergistic heat insulation and protection effect with the fire-retardant coating, further blocking the heat transfer generated by thermal runaway, strengthening the blocking effect on the high-temperature flames and heat sprayed from the narrow side of the electrode assembly, effectively suppressing the spread of thermal runaway to adjacent battery cells, and thus improving the overall safety protection capability of the battery cell and battery pack.

[0015] In one alternative embodiment, the fire-retardant coating is applied to the entire area of ​​the insulating diaphragm facing or away from the narrow side, or only to a portion of the insulating diaphragm facing or away from the narrow side.

[0016] Beneficial effects: On the one hand, the above-mentioned laying method provides diversified protection layout options. The laying range of the fireproof coating can be flexibly adjusted according to the actual application scenario, safety protection level, and cost control requirements of the battery cell. In high protection scenarios, the fireproof coating can be set in the corresponding area of ​​all insulating membranes to form a multi-layer flame-retardant and heat-insulating barrier, which enhances the blocking effect against high-temperature flames and heat sprayed from the narrow side. In conventional protection scenarios, the fireproof coating can be set only in the corresponding area of ​​some insulating membranes, which effectively controls the material cost of the fireproof coating while ensuring the basic fire protection effect, thus balancing the economy and protection of the battery cell. On the other hand, regardless of the laying method, the fireproof coating corresponds to the narrow side of the electrode group, which is a critical area for thermal runaway side spray. This ensures effective flame-retardant and heat-insulating protection of the core protection part, prevents the flame from burning through the shell and spreading to adjacent battery cells, and inhibits the chain reaction of thermal runaway. At the same time, in conjunction with the multi-layer insulating membrane stacked structure, it can further ensure the adhesion stability of the fireproof coating and ensure that its heat insulation and flame-retardant effect is stable. Under the premise of meeting different design requirements, it continuously improves the reliability of thermal runaway protection of the battery cell.

[0017] In one alternative embodiment, the first insulating film has a porous structure, and the material of the first insulating film is glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride.

[0018] Beneficial effects: On the one hand, the porous structure provides a good adhesion substrate for the fire-retardant coating, enabling the fire-retardant coating to effectively adhere to the pores and surface of the first insulating film, improving the bonding strength between the fire-retardant coating and the first insulating film, and preventing the fire-retardant coating from falling off or dropping during the stress process of battery cell assembly and use, thus ensuring the stable performance of the heat insulation and flame retardant effect of the fire-retardant coating; on the other hand, the selected materials such as glass fiber, non-woven fabric, and polyethylene have excellent insulation performance, high temperature resistance, and structural flexibility, which can fully meet the insulation protection requirements of the battery cell, reduce the risk of leakage and short circuit between the electrode group and the shell, and adapt to slight deformation and external force during battery cell assembly and use, making them less prone to damage. At the same time, the high temperature resistance of some materials can form a synergistic heat insulation effect with the fire-retardant coating, further improving the ability to block thermal runaway high-temperature flames and heat.

[0019] In one optional embodiment, the fire-retardant coating is a ceramic layer; and / or, the battery cell further includes a second insulating film wrapped around the outside of the first insulating film, the second insulating film being made of polypropylene or polyethylene.

[0020] Beneficial effects: The fireproof coating of this invention is a ceramic layer. The ceramic material has excellent high temperature resistance, heat insulation and flame retardant properties. It can effectively block the high temperature flame and heat sprayed from the narrow side when the battery cell is thermally runaway, forming a stable fire barrier and preventing the flame from burning through the shell and spreading to adjacent battery cells. At the same time, the porous structure of the ceramic layer and the first insulating film have good compatibility, strong adhesion stability, and are not easy to fall off and fail, ensuring that the fire protection effect continues to play a role.

[0021] This invention wraps a second insulating film around the outside of a first insulating film. This provides physical protection for the first insulating film and the fire-retardant coating, preventing damage or detachment during battery cell assembly and use due to external forces such as pressure and friction from the casing, thus ensuring the stable performance of the fire-retardant coating's heat insulation and flame-retardant effect. Furthermore, it enhances the overall insulation performance of the battery cell, reducing the risk of leakage and short circuits between the electrode assembly and the casing. The second insulating film is made of polypropylene or polyethylene. These materials not only possess excellent insulation properties, forming reliable secondary insulation protection outside the first insulating film and reducing the risk of leakage and short circuits between the electrode assembly and the casing, but also have good flexibility, abrasion resistance, and formability. They can tightly wrap the first insulating film and the fire-retardant coating, providing effective physical protection and preventing damage caused by external pressure and friction during assembly and use. Moreover, these materials have mature manufacturing processes, controllable costs, and are suitable for the needs of large-scale battery cell production.

[0022] Secondly, the present invention also provides a battery pack comprising: the aforementioned battery cell.

[0023] Beneficial effects: The battery pack of the present invention includes the battery cell as described above and has all the beneficial technical effects of the battery cell, which will not be repeated here. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention; Figure 2 for Figure 1 The diagram shows the structure of the battery cell without the first and second insulating films. Figure 3 for Figure 1 The diagram shows the structure of the battery cell wrapped with the first insulating film. Figure 4This is a schematic diagram of the structure of the present invention, which utilizes a shield to spray a fire-retardant coating onto the first insulating film. Figure 5 For fire-retardant coating set Figure 3 A schematic diagram of the structure on the first insulating film of the battery cell shown.

[0026] Explanation of reference numerals in the attached figures: 1. Pole group; 101. Narrow side; 102. Large surface; 2. First insulating film; 3. Fireproof coating; 4. Second insulating film; 5. Sheath; 501. Through hole. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The following is combined Figures 1 to 5 The embodiments of the present invention are described below. For ease of description thereafter, as follows... Figure 1 As shown, a spatial rectangular coordinate system is established: the height direction of pole group 1 extends along the Z direction; the length direction of pole group 1 extends along the X direction; and the width direction of pole group 1 extends along the Y direction.

[0029] According to an embodiment of the present invention, in one aspect, such as Figures 1 to 5 As shown, a battery cell is provided, including: a housing, an electrode group 1, a first insulating film 2, and a fire-retardant coating 3.

[0030] Specifically, the electrode assembly 1 is disposed within the housing, and the electrode assembly 1 has a pair of narrow side surfaces 101 disposed opposite each other along the X direction and a pair of large surfaces 102 disposed opposite each other along the Y direction; when there is only one electrode assembly 1, at least a portion of the first insulating film 2 is wrapped around the outside of the single electrode assembly 1 circumferentially along the XY plane; when there are multiple electrode assemblies 1, at least a portion of the first insulating film 2 is wrapped around the outside of multiple electrode assemblies 1 circumferentially along the XY plane; a fire-retardant coating 3 is disposed on the first insulating film 2, and at least a portion of the fire-retardant coating 3 is disposed opposite to the narrow side surfaces 101.

[0031] In this embodiment of the invention, a fire-retardant coating 3 is provided on the first insulating film 2 opposite to the narrow side 101, which can form a heat-insulating and flame-retardant barrier for the narrow side 101. When a single cell experiences thermal runaway, it can effectively prevent the high temperature and flame from spreading to adjacent cells, suppress the chain reaction of thermal runaway, and thus improve the overall safety of the cell and battery pack.

[0032] Specifically, such as Figure 1 and Figure 2 As shown, in this embodiment, the cross-sectional area of ​​the narrow side 101 is smaller than that of the large side 102. The reason for choosing to provide the fire-retardant coating 3 on one side of the narrow side 101 of the electrode assembly 1 in this embodiment is that a conventional electrode assembly 1 generally includes a positive electrode, a separator, and a negative electrode stacked along the Y direction. When thermal runaway occurs in the electrode assembly 1, the high-temperature gas, molten material, and flame inside are more likely to be ejected along the gaps in the X direction towards the narrow side 101 on both sides of the electrode assembly 1, making the narrow side 101 the area with the highest risk of thermal runaway ejection and the weakest protection.

[0033] Furthermore, such as Figure 4 and Figure 5 As shown, the fire-retardant coating 3 is disposed on the side of the first insulating film 2 closest to the electrode group 1; and / or, the fire-retardant coating 3 is disposed on the side of the first insulating film 2 away from the electrode group 1. It can be understood that by disposing the fire-retardant coating 3 on one or both sides of the first insulating film 2, this embodiment of the invention can form an effective heat-insulating and flame-retardant barrier between the electrode group 1 and the casing when thermal runaway occurs in the battery cell. This reduces the direct impact of high-temperature flames on the casing, reduces the risk of the casing being burned through, and effectively inhibits the spread of flames to adjacent battery cells, slows down the rate of thermal runaway propagation, and improves the overall safety of the battery cell and battery module. Simultaneously, the fire-retardant coating 3, combined with the first insulating film 2, ensures insulation protection while also considering structural compatibility, which is beneficial for meeting the requirements of battery cell coating and assembly processes.

[0034] It should be noted that this embodiment does not limit the manner in which the fire-retardant coating 3 is placed on the first insulating film 2, including but not limited to conventional processes such as coating, bonding, deposition, sputtering, printing, and impregnation. Any method that can stably place the fire-retardant coating 3 on the first insulating film 2 and meet the requirements of heat insulation, flame retardancy, and insulation protection should be covered within the protection scope of this embodiment.

[0035] Furthermore, in this embodiment, the fire-retardant coating 3 can be pre-formed on the first insulating film 2 and then covered together with the first insulating film 2 onto the side wall of the electrode assembly 1; alternatively, the fire-retardant coating 3 can be formed on a predetermined position of the first insulating film 2 after the first insulating film 2 has covered the electrode assembly 1. This embodiment does not impose any particular limitation on the forming and assembly sequence of the fire-retardant coating 3 and the first insulating film 2, as long as the heat insulation and flame-retardant protection function of the fire-retardant coating 3 in the corresponding area of ​​the narrow side 101 of the electrode assembly 1 can be achieved, it is within the protection scope of this embodiment.

[0036] For example, the fire-retardant coating 3 is pre-set on the first insulating film 2, so that the fire-retardant coating 3 and the first insulating film 2 can be integrated before the battery cell assembly. This is beneficial to improve the uniformity of coating thickness and adhesion stability. Then, the electrode group 1 is simultaneously wrapped with the first insulating film 2, which can simplify the battery cell assembly process, improve the wrapping accuracy and production efficiency, and avoid interference to the assembled components caused by subsequent on-site coating, further improving process controllability and product yield.

[0037] For example, such as Figure 4 and Figure 5 As shown, the fire-retardant coating 3 is formed at the position where the first insulating film 2 and the narrow side surface 101 of the electrode group 1 are opposite each other after the first insulating film 2 covers the electrode group 1. Specifically, the first insulating film 2 is first completely covered on the periphery of one or more electrode groups 1 in the XY plane, so that the first insulating film 2 and the pair of narrow side surfaces 101 and the pair of large surfaces 102 of the electrode group 1 are in close contact. Then, a shielding plate 5 is set on the side of the first insulating film 2 corresponding to the narrow side surface 101 of the electrode group 1. The shield 5 has a through hole 501 that penetrates through it. The projected outline of the through hole 501 matches the target area of ​​the fire-retardant coating 3 to be formed on the first insulating film 2. At the same time, the non-through hole 501 area of ​​the shield 5 effectively shields the remaining area of ​​the first insulating film 2 except for the narrow side 101, preventing the fire-retardant coating 3 from being sprayed onto non-target locations. Then, the nozzle of the spraying device is aligned with the through hole 501, and the fire-retardant coating 3 material is sprayed onto the target area of ​​the first insulating film 2. After the fire-retardant coating 3 has cured and formed, the shield 5 is removed.

[0038] In some embodiments, such as Figure 5 As shown, along the X direction, the orthographic projection of the fire-retardant coating 3 toward the narrow side 101 falls within the orthographic projection range of the narrow side 101. It can be understood that, along the X direction, this embodiment of the invention sets the orthographic projection of the fire-retardant coating 3 toward the narrow side 101 to fall within the orthographic projection range of the narrow side 101. This ensures effective isolation of the high-temperature flames and heat from thermal runaway splashes from the narrow side 101, preventing the flames from burning through the casing and spreading to adjacent battery cells. It also avoids ineffective application of the fire-retardant coating 3, rationally controlling the material and application range of the fire-retardant coating 3. While ensuring the protective effect, it also considers the structural compactness of the battery cell, and reduces problems such as decreased flexibility and easy cracking and material loss under stress caused by excessive application of the fire-retardant coating 3. This ensures the structural stability of the fire-retardant coating 3 during battery cell assembly and use, and ensures the continuous and effective performance of the heat insulation and flame retardant effect.

[0039] Furthermore, such as Figure 5As shown, on the YZ plane, the distance between the four periphery of the fire-retardant coating 3 and the edge of its adjacent narrow side 101 is w, and the value of w ranges from 1mm to 30mm. It can be understood that by limiting the value of the distance w to between 1mm and 30mm in this embodiment of the invention, the fire-retardant coating 3 can adapt to the battery cell housing structure, avoid assembly damage, and ensure the effectiveness of heat insulation and flame retardant protection, further improving the reliability of thermal runaway protection for the battery cell. Specifically, when w is not less than 1mm, it can effectively prevent interference and squeezing between the electrode group 1 and the housing R-angle during battery cell assembly, thus avoiding material loss and damage to the fire-retardant coating 3, ensuring the structural integrity and stable performance of the fire-retardant coating 3. When w is not greater than 30mm, it can ensure that the fire-retardant coating 3 provides sufficient coverage and protection to the narrow side 101 of the electrode group 1, preventing high-temperature flames and heat from leaking out through the protective gaps during thermal runaway due to insufficient coverage, effectively blocking the side-sprayed flame from burning through the housing and spreading heat to adjacent battery cells, and suppressing the occurrence of a thermal runaway chain reaction. Specifically, in this embodiment, the value of the interval w can be 1 mm, 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 17 mm, 20 mm, 23 mm, 25 mm, 27 mm, 28 mm, 29 mm, 30 mm, or any value range between the two.

[0040] It should be noted that the shell R-angle referred to in the above embodiments refers to the rounded corner structure formed by the rounded transition of the sharp corner position of the metal shell of the battery cell during the processing and forming process. Specifically, it is the rounded transition part at the intersection of the inner side wall and the end wall, and the inner side wall and the side wall of the shell. It is a structural design made by the shell to avoid stress concentration at sharp corners, improve structural strength and adapt to the assembly of the electrode group 1. This R-angle area is a key position where the electrode group 1 and the shell are prone to contact and compression during the assembly of the battery cell.

[0041] In some embodiments, the thickness of the fire-retardant coating 3 along the X direction ranges from 0.05 mm to 0.5 mm. It can be understood that limiting the thickness t of the fire-retardant coating 3 to between 0.05 mm and 0.5 mm in this embodiment of the invention balances the heat insulation and flame-retardant effect of the fire-retardant coating 3 with structural flexibility. Specifically, when the thickness is not less than 0.05 mm, it forms an effective protective barrier against thermal runaway high-temperature flames and heat, ensuring effective blocking of high-temperature heat sources sprayed from the narrow side 101 of the electrode assembly 1, preventing flames from burning through the casing and spreading to adjacent cells. When the thickness is not greater than 0.5 mm, it ensures that the fire-retardant coating 3 has good flexibility, preventing cracking, material loss, and other failures due to excessive thickness during cell assembly and use, ensuring the structural integrity and adhesion stability of the fire-retardant coating 3, while avoiding excessive coating thickness that increases the overall volume of the cell and affects its structural compactness. Under the premise of ensuring the effective performance of the core fire protection effect, it adapts to the structural design and actual application needs of the cell, improving the stability and reliability of the fire-retardant coating 3.

[0042] Specifically, in this embodiment, the thickness of the fire-retardant coating 3 can be 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.15 mm, 0.17 mm, 0.20 mm, 0.23 mm, 0.25 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.30 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or any value range between the two.

[0043] In some embodiments, the first insulating film 2 includes a plurality of insulating diaphragms, which are sequentially stacked along their thickness direction and wrapped around the outer side of one or more electrode groups 1 along the XY plane. It is understood that in this embodiment of the invention, the first insulating film 2 is configured as multiple insulating films that are sequentially stacked along the thickness direction and wrap around the periphery of the electrode assembly 1. On the one hand, this can form a multi-layer insulating protective structure, improve the insulation performance between the electrode assembly 1 and the shell, and effectively reduce the risk of leakage and short circuit inside the cell. On the other hand, the multi-layered insulating films can provide a more stable adhesion substrate for the fireproof coating 3, and the layered structure can disperse the external force compression and friction during the assembly and use of the cell, reduce the problem of peeling and damage of the fireproof coating 3 due to substrate damage, and ensure the stable performance of the heat insulation and flame retardant effect of the fireproof coating 3. At the same time, the stacked design of the multi-layered insulating films can form a synergistic heat insulation and protection effect with the fireproof coating 3, further blocking the heat transfer generated by thermal runaway, strengthening the blocking effect on the high-temperature flame and heat sprayed from the narrow side 101 of the electrode assembly 1, effectively suppressing the spread of thermal runaway to adjacent cells, and thus improving the overall safety protection capability of the cell and battery pack.

[0044] Furthermore, the fire-retardant coating 3 is applied to the area where all insulating membranes face or turn away from the narrow side 101, or only to a portion of the insulating membranes facing or turning away from the narrow side 101. This provides diverse protective layout options, allowing for flexible adjustment of the fire-retardant coating 3's application area based on the actual application scenario, safety protection level, and cost control requirements of the battery cell. In high-protection scenarios, the fire-retardant coating 3 can be applied to the corresponding area of ​​all insulating membranes, forming a multi-layered flame-retardant and heat-insulating barrier to enhance the blocking effect against high-temperature flames and heat sprayed from the narrow side 101. In scenarios with conventional protection requirements, the fire-retardant coating 3 can be applied only to the corresponding area of ​​a portion of the insulating membranes, effectively controlling the material cost of the fire-retardant coating 3 while ensuring basic fire protection, thus balancing the economic efficiency and protection of the battery cell. On the other hand, regardless of the laying method, the fireproof coating 3 corresponds to the narrow side 101 of the electrode group 1, which is a key area for thermal runaway side spraying. This ensures effective flame retardancy and heat insulation for the core protection parts, prevents flames from burning through the shell and spreading to adjacent cells, and suppresses the chain reaction of thermal runaway. At the same time, in conjunction with the multilayer insulating membrane stacked structure, it can further ensure the adhesion stability of the fireproof coating 3 and ensure that its heat insulation and flame retardant effect is stable. Under the premise of meeting different design requirements, it continuously improves the reliability of thermal runaway protection of the cells.

[0045] In some embodiments, the first insulating film 2 has a porous structure, and the material of the first insulating film 2 is glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. It can be understood that, on the one hand, the porous structure provides a good adhesion substrate for the fire-retardant coating 3, enabling the fire-retardant coating 3 to effectively adhere to the pores and surface of the first insulating film 2, improving the bonding strength between the fire-retardant coating 3 and the first insulating film 2, preventing the fire-retardant coating 3 from falling off or dropping during the stress process of battery cell assembly and use, and ensuring the stable performance of the heat insulation and flame retardant effect of the fire-retardant coating 3; on the other hand, the selected materials such as glass fiber, non-woven fabric, and polyethylene possess excellent insulation performance, high-temperature resistance, and structural flexibility, which can fully meet the insulation protection requirements of the battery cell, reduce the risk of leakage and short circuit between the electrode assembly 1 and the casing, and adapt to slight deformation and external forces during battery cell assembly and use, making them less prone to damage. Simultaneously, the high-temperature resistance of some materials can form a synergistic heat insulation effect with the fire-retardant coating 3, further enhancing the ability to block thermal runaway high-temperature flames and heat.

[0046] It should be noted that, in this embodiment, the porous structure of the first insulating film 2 refers to the presence of a large number of interconnected or independent micropores on the substrate of the first insulating film 2. These pores are naturally formed during the film forming process or are through holes 501 or micropore structures designed by the process. The pores are evenly distributed and the pore size is adapted to the adhesion requirements of the fireproof coating 3 raw material. This allows the fireproof coating 3 raw material to penetrate into the pores during the spraying process and form an interlocking bond with the film material, rather than just adhering to the surface of the film material. At the same time, this porous structure does not affect the insulation performance and structural strength of the first insulating film 2 itself, and can improve the bonding strength between the fireproof coating 3 and the first insulating film 2 while ensuring insulation protection.

[0047] Furthermore, in this embodiment, the first insulating film 2 can be directly adopted from the diaphragm in the conventional electrode assembly 1. This eliminates the need for specialized research and development and preparation of insulating film materials adapted to this embodiment, allowing direct reuse of the diaphragm commonly used in cell production. Its inherent porous structure meets the adsorption and adhesion requirements of the fire-retardant coating 3, while the insulation and high-temperature resistance properties of the existing diaphragm directly match the basic protection requirements of the periphery of the electrode assembly 1. Furthermore, this effectively simplifies the cell manufacturing process and reduces additional costs associated with film material development and procurement.

[0048] In some embodiments, the fire-retardant coating 3 is a ceramic layer; and / or, the battery cell further includes a second insulating film 4 wrapped around the outside of the first insulating film 2, the second insulating film 4 being made of polypropylene or polyethylene. It is understood that in this embodiment of the invention, the fire-retardant coating 3 is set as a ceramic layer. Ceramic materials possess excellent high-temperature resistance, heat insulation, and flame-retardant properties, effectively blocking high-temperature flames and heat from the narrow side 101 when the battery cell experiences thermal runaway, forming a stable fire barrier and preventing flames from burning through the casing and spreading to adjacent battery cells. Simultaneously, the ceramic layer has good compatibility with the porous structure of the first insulating film 2, strong adhesion stability, and is not easily detached or failed, ensuring the continuous performance of the fire protection effect.

[0049] Furthermore, in this embodiment of the invention, by wrapping a second insulating film 4 around the outside of the first insulating film 2, the first insulating film 2 and the fire-retardant coating 3 are physically protected, preventing damage or detachment during battery cell assembly and use due to external forces such as casing compression and friction, thus ensuring the stable performance of the heat insulation and flame retardant effect of the fire-retardant coating 3. On the other hand, this further improves the overall insulation performance of the battery cell, reducing the risk of leakage and short circuits between the electrode assembly 1 and the casing. The second insulating film 4 is made of polypropylene or polyethylene. These materials not only have excellent insulation properties, forming reliable secondary insulation protection on the outside of the first insulating film 2 and reducing the risk of leakage and short circuits between the electrode assembly 1 and the casing, but also possess good flexibility, abrasion resistance, and formability, allowing them to tightly wrap the first insulating film 2 and the fire-retardant coating 3, providing effective physical protection and preventing damage caused by external forces such as compression and friction during assembly and use. At the same time, these materials have mature technology, controllable costs, and are suitable for the needs of large-scale battery cell production.

[0050] According to an embodiment of the present invention, another aspect provides a battery pack comprising the aforementioned battery cells.

[0051] The battery pack of this invention includes the battery cell described above, and has all the beneficial technical effects of the battery cell, which will not be repeated here.

[0052] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that, include: case; An electrode assembly is disposed within the housing, the electrode assembly having a pair of narrow side surfaces opposite each other along the X direction and a pair of large surfaces opposite each other along the Y direction; A first insulating film, when the number of electrode groups is one, at least a portion of the first insulating film wraps around the outside of the single electrode group circumferentially along the XY plane; when the number of electrode groups is multiple, at least a portion of the first insulating film wraps around the outside of multiple electrode groups circumferentially along the XY plane. A fire-retardant coating is disposed on the first insulating film, at least a portion of which is disposed opposite to the narrow side surface.

2. The battery cell according to claim 1, characterized in that, The fire-retardant coating is disposed on the side of the first insulating film close to the electrode group; and / or, the fire-retardant coating is disposed on the side of the first insulating film away from the electrode group.

3. The battery cell according to claim 1, characterized in that, Along the X direction, the orthographic projection of the fire-retardant coating toward the narrow side falls within the orthographic projection range of the narrow side.

4. The battery cell according to claim 3, characterized in that, On the YZ plane, the distance between the four perimeters of the fireproof coating and the adjacent narrow side edge is w, and the value of w ranges from 1mm to 30mm.

5. The battery cell according to claim 1, characterized in that, Along the X direction, the thickness of the fire-retardant coating ranges from 0.05 mm to 0.5 mm.

6. The battery cell according to claim 1, characterized in that, The first insulating film includes multiple insulating diaphragms, which are stacked sequentially along their thickness direction and wrapped around the outer side of one or more electrode groups along the XY plane.

7. The battery cell according to claim 6, characterized in that, The fire-retardant coating is applied to the entire area of ​​the insulating membrane facing or away from the narrow side, or only to a portion of the insulating membrane facing or away from the narrow side.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The first insulating film has a porous structure and is made of glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride.

9. The battery cell according to any one of claims 1 to 7, characterized in that, The fire-retardant coating is a ceramic layer; and / or, the battery cell further includes a second insulating film wrapped around the outside of the first insulating film, the second insulating film being made of polypropylene or polyethylene.

10. A battery pack, characterized in that, include: The battery cell according to any one of claims 1 to 9.

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